Posted
by
timothyon Friday October 21, 2011 @07:36PM
from the if-you're-warm-you're-too-close dept.

An anonymous reader writes "I'm an American who is living in Tokyo. Stories have started popping up about 'radiation hot spots' in Tokyo and surrounding prefectures so I have begun to worry. I live on the first floor of my apartment building and right by our washing machine there is a gutter out there that is clogged with rain water and mud, which has me especially worried because my wife and I are planning to have kids soon. Obviously no one from the government is going to come by to check our gutter so I feel the need to take matters into my own hands. I have absolutely no idea so I'm asking you guys. What kind of radiation detector should I get? A Geiger Counter? If it measures Gamma rays is that enough? Are alpha and beta dangerous too? I know no one has all the answers regarding radiation but any advice you guys could give me would be great."

They're all pro-nuclear nuts here. They'd lie through their teeth about the risks if they thought it'd mean new reactors might get built.

It's hard to understand why human beings are so attached to one side of *every* question. Most people are almost completely unable to think straight because of hardened opinions, and cannot assimilate, much less evaluate, all data and points of view and draw conclusions. Unless they are basically experts in the field and have so much data and facts, that most of our one-sided opinions are classified as laughable religion and politics wars.

Even the Setagaya hotspot, caused by a forgotten stash of highly radioactive radium, which was orders of magnitude worse than anything else found in Tokyo, was nowhere near the point where it would have posed any danger to the people in the vicinity.

This is just not something which is worth worrying about, much less spending money on. Save your money for the thing your kid actually needs.

Additionally, any equipment sensitive enough to detect the trace amounts of radiation above background in a reliable manner is a) going to be rather expensive and b) need regular calibration (in the correct manner) to produce reliable and accurate results. The latter is the main reason why the whole 'citizen radiation map' thing differs wildly from the IAEA figures: buying a cheap GM tube off ebay is not the path to accurate measurements upon which health decisions should be based.

If this were any other topic that required technology, the majority of highly modded posts would point to various resources on how to approach the technology. Some posts would even include first hand accounts. However, if it is dealing with nuclear power, which apparently the majority of Slashdoters are completely sold on, the highest modded posts are, "don't bother." Any ideas on the discrepancy? If you LIKE the technology, then shouldn't you be trying to get more people involved? What geek hasn't wasted $300 on some device they didn't really need? Why is it not worth it this time and who are you to judge that for a fellow geek?

If you LIKE the technology, then shouldn't you be trying to get more people involved?

"The technology" is, in this case, radiation detectors. Now, it is true that I like radiation detectors quite a bit. However, I also realize they are expensive, hard to use, and of little to no value to the person asking the question, and thus the only advice I can honestly give is to not bother, as he would be throwing his money away based on a misunderstanding.

Alright, why not advise that he BORROWS one from an organization then? Like from Safecast [safecast.org]?

And what misunderstanding? Maybe he has a kid that likes to play and eat mud and he noticed the 57 microSv/hr hotspot in Kashiwa [nikkei.com]. Who knows wtf is going on around Tokyo, but woudn't a legitimate geek response be to scientifically test the area, just in case? Your response is either non-geek like (for a geek site) and/or just playing "nothing to see here, folks" shill-speak.

I do not have any information about place where you could borrow one, so I am unable to give any advice on that. What I said was, specifically, "Save your money".

I only just found out about the 57 microSv/h hotspot. That is indeed very interesting, but it is extremely unlikely to have anything to do with Fukushima, and sounds more like buried illegal radioactive waste, or maybe another forgotten stash of radioactive material that got buried by chance. That is something that could be found pretty much anywhere, and if you wouldn't worry about that living anywhere else, you shouldn't worry about it when living in Tokyo. The chances of encountering such a thing are quite minuscule.

Now, having citizens equipped with radiation monitors moving around measuring radiation is actually a very good idea, for exactly this reason: There is a lot of forgotten radioactive material around the world that it would be good to find, and lots of people moving doing lots of measurements helps with that. We saw this already with the Setagaya hotspot. However, this doesn't seem to be what the person asking the question is interested in. He just seems to want to measure radiation around his house, not over a larger area and not coordinated with others. This is basically useless.

but you were unaware of the first community of radiation monitoring enthusiasts? Care explaining why you considered yourself qualified to respond to his post then?

I was aware of them, but don't have specific information. However, contacting them would not help him, because he does not have a problem in the first place. He just has absolutely no need for a radiation detector.

"However, contacting them would not help him, because he does not have a problem in the first place"
Since when was scientific observation inferior to political dogma!? Maybe he would feel better having objective measurements rather than just trusting you, who has nothing to lose (and probably live thousands of miles away). Maybe that, in itself, has value to him.

Safecast have found it worth their time to start measuring parts of Tokyo [safecast.org]. Who knows what and where the yakuza have been dumping in the last 5

What he would be doing would not be scientific observation, and I what I was saying was not political dogma. Furthermore, your attitude has become unpleasant to the point where I am no longer interested in continuing this discussion.

Why would it not be scientific if he were to get help from Safecast? Would that not at least be more scientific that just believing your opinion that you claim is undeniable fact (based on zero actual observation)?

Dogma is defined as an opinion considered "unquestionably true" by the holder. Saying your post is not dogma alone, as if such a statement does not require specific supporting arguments because it is "unquestionably true," only strengthens the argument that you are just spewing dogma in this th

You have an incredibly unscientific view of what is and isn't scientific. Is there any benefit to having Science Olympiad students drop eggs off of buildings? No, not really. But we do it because A) they learn and B) it could pique their curiousity in other directions. The world is full of wonders you can measure and learn about, and some of them might end up not even matching the "official numbers" provided by the government - can you imagine that??? Shame on you for telling the poster not to check into so

Right, but you are still just throwing out assertions and statements without any supporting evidence in your posts. For instance, specifically where am I being rude and presumptuous? Oh, and more presumptuous than your statement that an area has no possibility of being radioactively contaminated even though no one has tested for radiation yet?

Just as a hypothetical, though, if one did have a defense mechanism towards having their own ideas challenged, wouldn't claiming the other party was being too rude

Would that not at least be more scientific that just believing your opinion that you claim is undeniable fact (based on zero actual observation)?

You're right. In fact, have you measured the area around your OWN home lately? No? Then you have zero evidence to suspect it's not hotter than Fukushima, drizzled in Chernobyle, and wrapped in the rubble from Three Mile Island. I suggested buying very expensive 24/7 monitoring equipment pronto. In fact, buy two to be safe. On the safe side you better buy 3. If you only buy two, and they disagree, how do you know which one is right?

You should do this immediately, and no longer waste your time posting to Slashdot. After all, you're wasting time that could be spent looking for things that might be radioactive in your neighborhood. I mean, shit.. There could be radioactive shit killing you RIGHT NOW, and you have zero reason to suspect there's not! Yes, run and hide. Run and hide. Then buy top notch monitoring equipment to protect you. It's the only scientific thing to do! I don't think I like the look of your neighbor's cat. Maybe it's been playing in a spent cancer treatment machine? It's happened before! Science will save you.

Or, if I were living in Tokyo like the original poster, I could measure my area for FREE with the help of the Safecast community [safecast.org], as I posted earlier. But never let trivial facts get in the way of your blind dogma . . .

And thanks for the confirmation that Slashdot is full of a bunch of pro-nuke shills who are so insecure that they cannot even have a rational, non-sensational discussion on public monitoring of radiation . . .

That is why Slashdot in broken when it comes to anything nuclear related . ..

It isn't broken. Slashdot is one of the few places where you can get rational discussion about nuclear energy - everywhere else is full of misinformation and fear-mongering. The parent is correct - any potential danger from radiation is overblown. Anyone being honest would tell the submitter that spending money on a geiger counter is completely unnecessary from a safety standpoint.

This isn't politics - this is honesty. Nuclear is safer than virtually all other sources of energy, radiation is a limited an

"Slashdot is one of the few places where you can get rational discussion about nuclear energy - everywhere else is full of misinformation and fear-mongering."
I believe the term you are looking for is "echo chamber." Yes, EVERYWHERE ELSE is fear-mongering. Slashdot . . . lead the way to eternal enlightenment . . .

"Anyone being honest would tell the submitter that spending money on a geiger counter is completely unnecessary from a safety standpoint."
Of course, let us completely ignore the possibility o

I was actually excited about the possibility of constructing a bomb out of some explosives and Tokyo mud. Talk about a dirty bomb!!!! (Dear FBI, I'm kidding, everyone knows you use the contents from old smoke detectors - still kidding!!!)

If you LIKE the technology, then shouldn't you be trying to get more people involved?

"The technology" is, in this case, radiation detectors. Now, it is true that I like radiation detectors quite a bit. However, I also realize they are expensive, hard to use, and of little to no value to the person asking the question, and thus the only advice I can honestly give is to not bother, as he would be throwing his money away based on a misunderstanding.

Radiation detectors are not that expensive ! You can pick up old ones on the cheap, or get a new one for $300.

A few pointers:

There are radiation detectors that measure alpha, beta and gamma depending on what shield is on top of the geiger counter.

The sensitivity of the detector depends on the volume of the geiger tube. Large ones (pancake, for example) are more expensive.

Most of the radiation is not that harmful, and the real danger comes from what manages to get inside, such as with food.

It is hard to figure out whether the food is dangerous with a regular detector as you need to integrate data from a high-sensitivity detector over a long time to be sure. This is also why a radon check takes tens of hours to do properly.

A sane thing to do with your own detector is to note the level of background radiation usual to where you live and check for any increases. There is usually variation depending on the time of the year (especially with a gas heater), weather, etc.

However, if it is dealing with nuclear power, which apparently the majority of Slashdoters are completely sold on, the highest modded posts are, "don't bother." Any ideas on the discrepancy?

Yes, the answer is this is a "side of the room" problem. It's essentially a form of tribalism. A "side of the room" problem is where a complex issue is divided into two sides, with no room in between. Each group tries to enforce a strict, and narrow viewpoint. Anyone outside of this narrow point of view is simply ign

Slashdot has educated people, with backgrounds in science, who understand the issues involved in nuclear processes.

Your implication is that there are two reasonable sides to the argument: pro-nuclear and anti-nuclear. This is akin to saying that there are two sides to the flat earth debate. The only difference is that everyone knows the flat earth people are wrong, but it takes a substantial amount of education to recognize how badly wrong the anti-nuclear crowd generally is.

As for the topic of this thread, the idea of asking for a geiger counter to measure some pool that is probably barely above background (if at all) would be like somebody asking if he needs to buy a set of 11 super-powered turbo fans for his home computer that he uses for email that has been running a little slow lately.. He can buy the fans, and there might be some marginal use to them, but the money would be better spent dealing with real problems.

Yes, I have a background in nuclear physics. No, I don't think it makes me biased, I think it makes me informed.

I love technology of all kinds. I am also working on a graduate degree in health physics (radiation protection would be the more appropriate title, fyi). Frankly, assuming this isn't someone trolling slashdot, he really shouldn't bother. The fact that he had to ask if alpha radiation was a significant concern tells me he isn't even close to qualified to assess the risks a radioactive source poses.

Think of it this way.. If someone asked you "I want to write my own TV database scraper. What would the best type of programming language to learn be? Will I need a keyboard? Just fyi, I only have a small amount of time, as this isn't my career," what would your response be? The question he asked is on the same level. If you don't immediately recognize that, then you really have no business commenting on the subject. It would be like someone asking for the best statistical thermodynamics textbook, then making it apparent they didn't know basic algebra.

Ignoring for a second the obvious serious lack of knowledge, radiation monitoring equiptment of any quality is expensive and needs calibration. Which requires access to radioactive standard sources. A geiger counter tells you nothing, especially a crappy one. I have a natural uranium deposit not far from my home. A geiger counter would light up like a christmas tree near it. If you didn't understand what what was going on, or even worse, didn't have any understanding past "the needle is moving, oh no!", then the results would be at best worthless and at worst misleading. And in the end someone untrained would have wasted thousands of dollars for no reason.

Believe it or not radiation is a complex and not at all obvious thing. Most people haven't studied it in any significant fashion, in a university or otherwise. In the same way a doctor would never encourage someone to self diagnose, I would never encourage someone to measure radioactive exposure by themseves. It would be irresponsible for me to do so. And excuse all the comparisons, but I occasionally go to public outreach meetings and have become aware that people need things put in terms they understand. Especially smart people. Smart people tend to form an ignorant view, assume they are right, then assume some kind of conspiracy when they are informed they are wrong.

Personally, I thing ignorant people *should* be learning about and experimenting with radiation detection equipment. The lack of understanding causes a huge amount of trouble, and this is how people learn. And telling people that they are too uneducated to ever understand this stuff is exactly why the public refuses to trust us when we say that they don't need to worry about Fukishema unless they are next door.

What they need to be told at the same time they start to measure radiation is Don't Panic. The g

You have this wrong. When people have asked questions where the answer is "don't do it", people have said "don't do it.". That is the right answer in this case.

First, if someone said, for instance, "What 8-core server do you recommend for me to run my personal web site on?" The answer would also be "Don't bother." Same here. People have hysteria over "radiation", when low levels are simply not harmful.

If he lives in eastern Tokyo metropolitan area there is a slim chance that he indeed have something to worry about like in Chiba or in Saitama. If he lives in western Tokyo he doesn't have absolutely nothing to worry about. Levels in Tokyo in practical terms are at the same level than before the disaster. It would have been helpful if the poster wrote in which zone lives. The MEXT readings in the previous format put Bunkyo-ku as Tokyo's ward with the highest readings, but still not something to worry about.

Still, I liked more the previous graph version that MEXT had under prime minister Kan since it clearly put visual info about the highest levels recorded by prefecture, the normal recorded levels and the current levels.

I am totally optimistic that we can solve the world's resource problems, class warfare, engineered famines, etc by breaking the cycle of mindless procreation by people who don't have their heads on straight.

Your math is suspect. The probability of a child being a genius is more or less a constant. The more children are born, the more geniuses are among us. One genius can invent a Warp drive, or LENR, or a neural network for machine intelligence for the whole civilization. By limiting the population you r

Or even better...spend the money on a vasectomy. It isn't fair to have a child who will be severely disadvantaged in this world by a naive, scared, lazy parent. You shouldn't have kids.

Also clean your gutters.

This is why fuckwits such as yourself shouldn't be allowed to control who has children. Your comments are nothing short vicious abuse, based on a single submission by a poster. By your logic your own troll means that you should not breed. Clearly you are too aggressive, judgemental and self important. So clean your own fucking gutters before telling others to..Me, I don't pretend I should decide who gets to breed. And this cheap shot piece of MANURE post gets modded as insightful . For shame slashdot!

When they talk about "radiation hot spots", they're not talking about anything that will be a problem unless you're standing on it 24/7 for a decade or so.

But, to provide more detail, alpha isn't a problem unless you eat the emitter (or inhale it), beta isn't a problem unless the emitter is in contact with your bare skin, and gamma can be a problem, assuming you live next to it for a while....

True, but that's usually the problem - alpha emitters getting into air or food. A gamma emitter big enough to be a hazard is easy to detect and tends to be noticed. [bousai.ne.jp] Japan has a decent monitoring system, and the US has a paranoid one since 9/11.
(Back in 1983, there was an incident where a scrapyard in Mexico got a big cobalt-60 radiation source [webcitation.org] and recycled it into steel. Radiation detectors then went in at US border crossings.)

Monitoring milk is a good check for airborne radioactives, because cows conc

The body treats radioactive isotopes like any other particles: when ingested, it expells them almost immediately. There are specific exceptions, like iodine 131, that the body can mistake for the normal isotope (because your body only wants the iodine, the form means nothing), but even those are only harmful if ingested in very large quantities.

As an example, the posterchild for nuclear disaster, Chernobly, mostly resulted in a few dozen cancer deaths in children from iodine 131. Cows which eat grass cove

You already have a lot of radioactive particles in you, have fun panicking. The body does have mechanisms for dealing with genetic damage.

Essentially you spend time and effort worrying about things that will never impact you and ignore all the things that do impact you. Then you try to claim that you're being prudent rather than a hypocritical moron. In that case, there's a lot more you should be concerned about. I mean, I hope you avoid living or being anywhere near a coal power plant as well, lots of uran

There is an app for that: https://market.android.com/details?id=com.rdklein.radioactivity - and no, it's not one of those fake geiger counter apps, but instead a clever hack using the CCD of the internal camera for detecting beta and gamma radiation. All you have to do is cover the camera, so only radiation events will show up on the CCD. The app counts the events and checks against an established calibration table.

You should contact Safecast [safecast.org]. I believe they will even lend you a device and the data will be incorporated into their map.

Oh, yeah, and you asking Slashdot this question is like asking PETA how to skin a deer. Hope you have the persistence to scan through all the highly modded posts insulting your intelligence to actually find useful answers to your question . . .

Rather than geiger counter, there are plenty of electronic pocket dosimeters which can also show accumulated dose. Your main concern is measuring gamma. These dosimeters will run from $200 to $600 for a basic model. Some even can show dose rate graph over time. http://www.dosimeter.com/survey-meters/digilert-100-survey-meter/ [dosimeter.com]

There are some bulky Geiger counter wristwatches you can buy. Polimaster makes some, for example. They're pricey, but they'll do that job. An alarm goes off if it detects too many Sv, which you can set after establishing a baseline for where you live. Since it's a small counter, it takes about a minute for it to accumulate enough statistics to warn you.

Just never take the thing on a flight. It'll beep without end at high altitude. If you explain why it's beeping, you'll be detained.

Well, what the best device is depends on what it is you want to measure. Alpha particles are not harmful if on the outside - they can't penetrate the skin - but can be exceptionally nasty if ingested. Beta particles can travel further and through more, but still aren't exceptionally dangerous at the kinds of doses you're likely talking about. Even radioactive particles that emit gamma aren't dangerous in low quantities.

The limestone caves in the Peak District are considered dangerous enough that guides can't go down them on consecutive tours and sections are off-limits to potholers. You should probably wait 10-15 mins after going on a tour before getting into a car if there's a group of you. The source of the radioactivity is a mix of uranium-containing ores and radon-bearing igneous rocks. If you were to encounter anything comparable in Tokyo, you'd be in serious trouble,

In reality, the biggest hot-spot reported to date was due to antiques. In all probability, uranium ore (a very popular mineral for adding a yellow tint to glazes and glass in the 1800s and early 1900s) would be what was found, although depending on the instruments used, radon-based paints (very popular for its glow-in-the-dark properties) is another strong possibility. Neither could be considered remotely a health hazard to your average citizen. In fact, given the volcanic nature of Japan, radon-bearing rocks are almost certainly your number 1 health hazard. For that, you'd want a Geiger counter (only if paranoid) and a decent extraction fan (radon is a gas).

If you're worried about fallout, then put a small plastic tray on the roof to collect rain and borrow a Geiger counter. If the rainfall contains nothing of significance now, then it won't do in the future. It takes a LOT to put something as heavy as dust as high up as the cloud layer.

If you are absolutely paranoid, take a roll of 35mm film into a pitch-black room and unroll it. Cut it into squares. Put each square between two pieces of cardboard that are just thick enough that absolutely no light will get through. Use duct tape round the edges to seal the sandwich up. Radioactive dust is the biggest problem and dust is worst in the corners of rooms, since they're hard to clean. Put a film sandwich in all the corners in your house. Leave them there for, say, about a week. Gather them up and take them to anyone with a darkroom to develop. If the squares are completely fogged over, THEN you can worry. And buy a better vaccuum cleaner. If the film shows little or nothing, then you can be absolutely certain that the only thing that you're in danger of is a heart attack from self-induced stress.

You cannot do this at home. The equipment you can afford (and use) will basically be able to tell you when to run, but that is it. Radioactive substances have highly different toxicity and the direct radiation effect is often not what counts. Example: Plutonium is completely harmless unless ingested. You skin shields completely against its radiation. However when ingested, if comes close to cells and becomes the most deadly substance known to mankind. Also, air happens to shield its radiation! So measuring it requires a very, very thin layer of the substance to be measures, or better vacuum. And very specialized and expensive equipment.

I advise to invest the effort instead in healthy living. If you can, move far away from Tokyo. Other than that you best bet is to hope for the best.

I asked about this on here not too long ago and was advised that the actual test procedure is to have a fan, and a filter, and to test the filter for particles. It seems to me like you could put a remote sensor in a little wind tunnel with a fan at the back and a filter at the front. You can buy an aerosol cleaning spray intended to remove radioactive particulates from the sensor, but you can also just put it in a plastic bag to prevent it from becoming contaminated itself. You can get medical grade air fil

You actually have to incinerate that filter to measure what was caught in it.

On the Geiger-counter edge, a normal Geiger-counter does only measure count, not intensity. Yet intensity is critical to identifying what you actually have in your sample. A count of alpha or Beta particles or Gamma rays does not tell you a lot. It basically just tells you "get out here fast" if it is high. The second problem is that Geiger-counter tubes change over time. So what you actually do in a real measurement is first calib

Well, TLDs are cheap. It's just the equipment to process them that's expensive! They're the first-line monitoring device in nuke power plants. Employees where them on the job for a month, and they get turned-in.

As others have noted, ingesting the material is hazardous. This includes inhaling the material. Wear a face filter if dealing with anything suspicious like that.
Otherwise, consider putting on rubber gloves with the mask, and removing the gunk from the gutter to somewhere safely away from you.

Some time ago (when I almost had time to do such things) I calculated the dose one receives from the average banana. Here's how it goes:

On page 620 of the CRD Handbook on Rad Measurement and Protection, the concentration of K-40 in a "Reference Banana" is listed as 3520 picocuries per kilogram of banana. For those of us who are stuck in certain unit ruts, this is equivalent to 3.52E-6 microcuries of K-40 per gram of banana.

Federal Guidance Report #11 lists the ingestion dose (committed effective dose equivalent) for K-40 as 5.02E-9 Sv/Bq or (again, for those of us who are "unit-challenged," 1.86E-2 rem per microcurie ingested.)

Thus, the CEDE from ingestion of a Reference Banana is 5.28E-4 x 1.86E-2 = 9.82E-6 rem or about 0.01 millirem.

I have found this "Banana Equivalent Dose" very useful in attempting to explain infinitesmal doses (and corresponding infinitesmal risks) to members of the public. (Interestingly, the anti-nukes just HATE this, and severely critisize us for using such a deceptive concept.)

Would love to go into more detail, but have to get back to our DEADLY Human Radiation Experiments (i.e., eating bananas.)

The same table in the CRC Handbook lists 3400 pCi/kg for white potatoes and 4450 pCi/kg for sweet potatoes - so you could carry through the same sort of calculation for Reference Potatoes. Interestingly, raw lima beans come in at 4640 pCi/kg, "dry, sweet" coconut comes in at 6400 pCi/kg, and raw spinach
(yum!) comes in at 6500 pCi/kg.

Considering the fact that the DOE has officially stated that "there is no safe dose of radiation" my advice to you all is to stop eating immediately.

Oh yes! Almost forgot. Regarding K-40, go into your local grocery store, buy some salt-substitute (there are two common brands, and the one in the white and orange labeled container works best) spread some out on a table and check it out with a GM survey instrument. There it is folks, deadly radioactivity in your grocery store!

Neither Lawrence Livermore National Laboratory, the University of California, nor the Department of Energy recommends eating bananas.

-------
The point of course, is to make people realize that the notion that "there is no safe dose of radiation" isn't necessarily correct. Your granite countertops have trace particles of uranium in them. The Capital Building in Washington DC has so much granite in it that it wouldn't be qualified as a nuclear facility because it already emits too much radiation. We consume radiation all of the time from a variety of sources and our bodies rid themselves of it naturally.

....The point of course, is to make people realize that the notion that "there is no safe dose of radiation" isn't necessarily correct. Your granite countertops have trace particles of uranium in them. The Capital Building in Washington DC has so much granite in it that it wouldn't be qualified as a nuclear facility because it already emits too much radiation. We consume radiation all of the time from a variety of sources and our bodies rid themselves of it naturally.

That has to be the best way to trivialise the argument I have ever seen.:-)
um but we aren't talking about bananas and granite here we are talking about people and are you able to defend your argument better than just talking about and hiding behind the trivial ?

(Interestingly, the anti-nukes just HATE this, and severely critisize us for using such a deceptive concept.)

Well, that might actually be because you have your facts wrong. BTW, I have a PhD in physics, my specialty is nuclear physics, I am very much in favor of nuclear power, and I think the radiation issues at Fukushima were ridiculously overblown. But nevertheless that doesn't affect the reality that your facts are wrong.

The body has systems that regulate the amount of potassium it holds. If you ingest more potassium, your body immediately detects that and immediately excretes the excess in your urine. Therefore ingesting a banana has essentially no effect on your radiation exposure. For a very short time, you have a slightly higher than normal amount of potassium in your body. Then it goes back down. The integrated excess dose turns out to be negligible compared to natural background.

If you want an example that's scientifically correct, here are some:

sleeping in the same bed as someone else for one month =.001 mSv (not that this will be an issue for slashdotters)

eating a pound of Brazil nuts =.001 mSv

long plane flight =.1 mSv

CT scan = 10 mSv

dose needed to cause mild radiation sickness = 1000 mSv in a short time

maximum excess rate of exposure for people in Tokyo due to Fukushima =.001 mSv/hr

Unfortunately, for all of us, that particular text was compiled and put into print on March 26, 1986, long after the US, the Soviet Union and other countries had already set off more then 2,000 nuclear explosions during testing. Is that taken into consideration when measuring radiation in a banana?

Your banana is really more of a "relative reference banana", is it not?

For that matter, I was shocked to discover that porcelain teeth emit a surprising* amount of radiation. For a 5th grade science fair project, I took a handful of dental X-ray films (my father is a dentist) and attached them to various everyday objects folks (or 5th grade kids) might be suspicious of emitting radiation, then developed them in batch after one month of exposure. For the youngsters who have never seen a dental x-ray using real film, they are small (about 4x5cm) squares of photographic film seal

I was going to echo the general attitude that the fears are probably misguided, but somewhere in the Church literature (I'm "Mormon") I was reading several months back, I noted that we had sent a bunch of radiation detectors to the Touhoku area.

So they apparently are either taking the risk seriously, or they are wanting to provide our members with a way to check and avoid unnecessary worries.

So the story others have pointed towards talks about a "neutron hotspot" someone found. The measured level of neutron radiation is 464 nano-Sieverts/hour. That's an annual dose of 464*24*365= about 4 million nano-sieverts/year, or 4 milli-sieverts/year. Background radiation varies in the world from around 2-6 milli-sieverts/year. So essentially the additional neutron radiation is about equal to a normal background radiation. Basically these so called "hot-spots" are completely harmless. If you're espe

Adafruit.com [adafruit.com] sells a Geiger counter kit. They specifically state that it's not for life-or-death situations, but it sounds to me like all you really need is a little peace of mind. For $99, plus shipping and a little elbow grease, this should do the trick.

If, on the other hand, you have reasonable cause to think that there is a real threat in your area, then disregard my suggestion. I don't know enough about the subject to provide the answers you need.

Here is a way to build your own radiation detector to check a sample.http://www.youtube.com/watch?v=RVj69R66Agg [youtube.com]
The coolant used is an air duster can turned upside down. Any self respecting slashdotter should have one of these.
So basically what you need is isopropyl alcohol 99%, a clear sided container with the bottom painted black, a bright flashlight, a small rag or tissue, and an air duster can.
Should be able to build it in 10 minutes. If you have a hot source you will see many streaks of radiation. With background radiation you will only get the occasional streak. Maybe one every 20 seconds.

You used to be able to get a Geiger counter on eBay for well under $100 (which is itself a rip-off because in Eastern Europe they are really cheap). After Fukushima people went crazy in countries as far away as America thanks to our media's 24-hour *F*E*A*R* cycle. Prices jumped up to $1000 and were sold out for many months in advance. They've fallen back to $400. Still a rip-off, but wait and they will keep falling.

They have Geiger Counters at most government facilities now and will come and check areas of concern. Out of curiosity I went to a nearby civic center and had my cars air filter checked out after I drove through Fukushima (on the Touhoku expressway) and it didn't read higher than normal. Then a week ago there were concerns over mushrooms from the area and my wife had some checked out. It's not just government facilities offering the service - depending on where you are community centers and other groups, su

There were 2 radionucleides released which are particularly important: iodine-131 and cesium-137. Of those, ioidine-131 is about 1000x more radioactive and has a half-life of about 8 days. It has already done its damage and decayed. Only 0.01% remains. In other words, the horse has already left the barn. If you wanted to do something, then the time to do so was within 2 weeks after the meltdown.

Greenpeace Japan just came out with a report on supermarkets a couple days ago and they are pro-consumer.They might have some info.Generally the radiation went over Tokyo and landed in Shizuoka destroying the green tea crop.There are a couple hotspots though the main one I think is some idiot who was storing bottles of radioactive water.I doubt your gutter is a problem but then again you could clean it out..The main issue for you is that for infants, extremely slight contamination of Tokyo water, shellfish

First and foremost, as others have posted this is too late to worry about it, AND there is nothing to really worry about.

BUT, if you want to approach this as a fun sort of science-fair project that will only tell you 'IF' and not 'HOW MUCH', read on.

You have 3 dirt-cheap and easy ways to detect radioactivity:

1) take an unexposed roll of film (B&W might make it easier to see) and place it near to suspected source. Go develop the film. If you see alot of 'static' then there might be something there. (make sure the place that develops it does the whole roll and doesn't try to malipulate/enhance the image for you) Tell them you will pay for all frames including the 'blank' ones. *For bonus points, you make a frame that you can mount strips of unexposed film to and 'aim' the film at the suspect areas. (make sure you keep the film away from the light)

2) (must be done at night) grab an old phosphor screen (like from an old television), as radiation hits it you will see small flashes of light like static

3) Use a smoke detector. as beta particles pass through the detector, the alarm will go off

If Mr/Ms Anonymous wishes to contact me, I can check the gutter etc for him/her. I've checked out friends' places in Chiba and elsewhere. Immediately after Fukushima, prices on detectors rocketed past $1200; now they're back down around $300 and in plentifu supply.
The cheapest sensible devices available in Japan at the moment are probably one of the Soeks range. This is a detector, not dosimeter. It doesn't log data, and there's no PC connectivity, for example.It only runs 10 hours on a battery, though.
For dosimeter, the DosRAE2 is readily available and, again, reasonably priced. It runs 400 hours between recharges and is designed to be worn as a badge. Lots of alarms. The PC software for logging data and managine multiple DosRAE2 badges is laughably bad, though.
If you really want one of these things, I'd definitely go for the simple geiger counter (i.e. Soeks), because you get a very visual idea of what's going on around you. Many of the people using these things around Japan aren't capable of interpreting the results.
Hotspots within Tokyo: not seen anything comparable to yer average granite lobby, and nothing anywhere near, say, Colorado.

There are three types of radiation you have to deal with when it comes to fallout. Alpha, beta, and gamma.

Alpha radiation can't even go very far through the air. Few inches give or take. It isn't dangerous to you at all unless ingested.

Beta radiation goes a little farther but isn't dangerous unless very concentrated and close, or is ingested.

Gamma radiation is what you would have to worry about the most, but significant levels aren't going to accumulate near you unless you're directly in the path of the fallout. In which case there would likely be much higher radiation readings between you and the plant.

As for alpha and beta, you won't be able to easily test for these. These are mostly rather transient in nature. Gamma rays you can easily test for, just buy a Geiger counter online and make sure it works. Your local university would probably be glad to help you calibrate it, talk to the physics or nuclear engineering department.

yes you are right this "background" radiation does occur naturally and no your are wrong their is reason to fear as their is no known safe level of radiation.

This so called "natural" radiation is thought to be the causes of some cancers.

"...most scientists and regulatory agencies agree that even small doses of ionizing radiation increase cancer risk, although by a very small amount. In general, the risk of cancer from radiation exposure increases as the dose of radiation increases. Likewise, the lower the exposure is, the smaller the increase in risk. But there is no threshold below which ionizing radiation is thought to be totally safe."

Our body has mechanisms to deal with cellular and genetic damage to a certain extent. Eventually something will kill you, worry about what is likely to kill you and not what kills out guy out of fifty million.

most scientists and regulatory agencies agree that even small doses of ionizing radiation increase cancer risk, although by a very small amount.

Actually, "most" is probably overstating the case. This is called the linear-no-threshold model, and it the model which has been in use so far, because it is the one that is the most cautious. However, there is not enough data to to support it. It was chose out of caution, not based on evidence.

As data slowly accumulates, people are starting to lean towards the view that it is, in fact, not correct. Small exposures to radiation do not seem to cause harm. This is likely due the body's repair systems, evolved

yes you are right this "background" radiation does occur naturally and no your are wrong their is reason to fear as their is no known safe level of radiation.

This so called "natural" radiation is thought to be the causes of some cancers.

"...most scientists and regulatory agencies agree that even small doses of ionizing radiation increase cancer risk, although by a very small amount. In general, the risk of cancer from radiation exposure increases as the dose of radiation increases. Likewise, the lower the exposure is, the smaller the increase in risk. But there is no threshold below which ionizing radiation is thought to be totally safe."

Maybe, but the risk is utterly not worth worrying about. Every second of your life you have ~5000 decays of potassium 40 within your body. If you were to remove that potassium you would die. A few tens of becquerels of extra radiation external to your body is a ridiculously small extra risk.

yes you are right this "background" radiation does occur naturally and no your are wrong their is reason to fear as their is no known safe level of radiation.

Utter BULLSHIT..

There is NO LINK between cancer and radiation in humans at below 100mSv/yr acute radiation dosage or 400mSv/yr prolonged radiation dosage or 4000mSv/lifetime (you can't exceed either of the limits). Period.

And now you are trying to spin this into "there is no known safe level of radiation"??? Seriously. Get a life. Radiation is a *stressor* like 1000s of other things that are far more carcinogenic that you choose to expose yourself to. WTF do you think formaldehyde does to you? Or gasoline? Or submicron dust from car breaks on the street?? All of these are far more dangerous than radiation because these target specific areas of your body.

There is NO KNOWN TOTALLY SAFE LEVELS OF BREATHING OXYGEN. Oxygen is the strongest free radical creator in our body. Now go, and deal with it.

You sound like someone that can't understand that they do not live forever. Hell, I hope you do not drive or get out of the house as that is far more dangerous than if you didn't evacuate from Fukushima and and proceeded to lived 2km from the reactor for next 100 years. But I guess sometimes it is futile to explain magnitude of danger if people have preexisting dogma about something.

"There is no totally safe level of radiation" just like it is not totally safe sitting on your ass typing this up. Yeap, nothing is totally safe.... Geez!

Other posters have pointed out that this is the linear no threshold model, and we use it because it is the worst case scenario. Honestly, it is probably wrong. In fact, there has been recent speculation based on data from areas of the country with high natural radon concentrations that small doses of radiation are good for you. The theory goes that a small dose stimulates your body's natural genetic repair mechamisms, thus decreasing cancer occurance across the board.

I'll give you a good comparison: If you live in Mexico City (about 2km above sea level), you get more radiation then you got in Tokyo in any day during or after Fukushima due to having 2km less atmosphere buffering radiation from the Sun.

Fun part? There is no statistical cancer or child birth defect spike in Mexico City in comparison to any other city.

Fukushima-diary reports that a neutron ray was measured in Tokyo. Neutron ray is emitted from Uranium 235 wich came from MOX with Plutonium and can not be measured by most of the Geiger counters.

Neutrons come from fission, fusion or radioactive decay. All of these processes produce photons and electrons which are detected by geiger counters. If a significant neutron flux was being produced, whatever was producing them would be sending geiger counters crazy.

Perhaps you should educate yourself in basic physics rather than passing on the unfounded ravings of crazy people?

FWIW, in the week of the meltdown exactly one significant neutron flux was detected. This was probably caused by a prompt criticalit

I hope that was a sarcastic post. U-235 has a half-life of 700 million years which is the only reason that there is any left around in nature. As such it is barely radioactive. The only time you have to worry about it is if there is so much that it is near a critical mass (=52kg sphere) or if you are likely to eat it since it is highly toxic.

I hope that was a sarcastic post. U-235 has a half-life of 700 million years which is the only reason that there is any left around in nature. As such it is barely radioactive. The only time you have to worry about it is if there is so much that it is near a critical mass (=52kg sphere) or if you are likely to eat it since it is highly toxic.

I dont know about the 700 million years part but I do know that all reactor fuel is made from U-235 and is very toxic and radioactive.

perhaps
you are talking about U-238 which is 99.99 % percent of the form of uranium (apologies to uni lecturers out there but its close enough)
we get on earth the U-235 makes up the other 0.1% which is why you have to enrich the uranium before you can use use it.

I dont know about the 700 million years part but I do know that all reactor fuel is made from U-235 and is very toxic and radioactive.

It is only highly radioactive AFTER it has been inside the reactor for a while. The radioactivity comes from the fission products which are neutron rich nuclei and so decay via beta decay. These are not produced in any significant quantity outside the reactor core because the U-235 neutron capture cross-section is ~1,000 times smaller for fast neutrons and so there is no noticeable chain reaction from a spontaneous fission event. Before the fuel is in the reactor it only poses a toxic hazard.

If you want proof have a look at this picture [wikipedia.org]. It is someone wearing latex gloves and holding a uranium fuel pellet in front of a container of hundreds of fuel pellets. While this is safe for fresh pellets you would not do this after these pellets have been in the reactor core. Indeed when spent fuel rods (containing the pellets) are removed from a reactor they are stored at the bottom of a pool for a period so some of the radioactive fission products to decay because the fuel is so active.

u-235 doesn't emit "neutron rays", it decays by alpha emission into Th-231, with a half life of 700 million years. You can even hold a piece of the metal in your hand, wearing just the gloves of a rad suit so you don't have ingestible particles left on your skin. Sure, in a running reactor or exploding old-style fission bomb it can absorb neutron and then fission into many things including neutrons, but there are no exploding reactors or atomic bombs in Tokyo. In general, you need never worry about neu

I've an even better one, I have sitting here two 10" uranium glass plates, of which of course 0.72% is U-235. The former owners, relatives of mine who gave it too me to make my geiger counter do something fun and interesting for my kids, ate meals off the stuff for decades since they were married. They are in their 80s, that U-235 must be a really slow poison! ha!

Because alpha radiation doesn't penetrate well, simple proximity to an alpha source isn't a big deal; but if you manage to absorb an alpha emitter, the alpha radiation no longer has to penetrate well to cause significant damage(just ask the late Mr. Litvinenko).

Effectively, alpha emitters have to be handled as though they possess pretty extreme chemical toxicity. Properly sealed sources are pretty much harmless. Dusts, dissolved compounds,

Alpha emitters should be approached with considerable caution:
Because alpha radiation doesn't penetrate well, simple proximity to an alpha source isn't a big deal; but if you manage to absorb an alpha emitter, the alpha radiation no longer has to penetrate well to cause significant damage(just ask the late Mr. Litvinenko).
Effectively, alpha emitters have to be handled as though they possess pretty extreme chemical toxicity. Properly sealed sources are pretty much harmless. Dusts, dissolved compounds, aerosols, etc. are to be avoided.

Yes this the reason why Chernobyl is off limits and if you visit you have to wear a dust mask because if you get one speck of contaminated dust in your lungs
your toast.

My guess is that 20-25% of the readership of Slashdot has studied enough physics or radiochemistry to have all the answers as pertains anyone in Tokyo. Possibly more, as it was a good portion of the A-level physics syllabus when I was in school and if you wanted to go to University you typically took one of the traditional hard sciences (at least) regardless of what you were applying for.

I have the minor added advantage that my A-level computing project was a radioisotope identification expert system (you f

In other words, there should be 100,000+ people on Slashdot who could write a University-grade paper on everything the original poster asked.

But even assuming you're right, that leaves 10,000,000+ who know bugger-all about it but might nevertheless post an answer; from the fact that he asked in the first place, we can assume that the questioner will have trouble distinguishing the two.

To the OP: as the proud recipient of an A grade in A-level physics, I'd advise wrapping the baby in aluminium foil, and re-aligning the gutter to improve the flow of chi energy into your washing machine.

There might even be a few of us here who have some actual experience in radcon and health physics. You just have to be careful to take our advice and not the advice of the others who don't know quite as much, who in a perfect world would keep quiet, but in the real world many of whom will have a lot to say.